Improving lubricating oils by adsorption



IMPROVING LUBRICATING OILS BY ADSORPTION Roy E. Thorpe, San Francisco, Robert J. Moore, Orinda, and Clarence Lynn Mahoney, Berkeley, Calif., assignors to Shell Development Company, Emeryville, Calif., a corporation of Delaware No Drawing. Application May 18, 1953, SerialNo. 355,868

6 Claims. (Cl. 196-147) This invention relates to a method of treating lubricating oil fractions with a solid adsorbent to remove therefrom components having undesirable viscosity characteristics. More particularly, it relates to the production of high quality lubricating oils by adsorption with a silica gel. oilcompositions.

It has generally been considered that the saturated components (the parafiins and naphthenes) ofa lubrieating oil are the high viscosity index (V. I.) components, and that the aromatic components are the low V. I. components. Therefore, it has been proposed to treat a lubricating oil fraction to remove the aromatics therefrom, and thus increase the V. I. of the fraction. One of the methods employed involves subjecting the lubricating oil fraction to selective adsorption with a solid adsorbent, such as silica gel, activated charcoal,

etc.,, the adsorbent having an afiinity for the various hydrocarbons in the following increasing order: saturates, olefins, and aromatics.

It has now been found that certain components of the saturate fraction of a lubricating oil fraction have undesirable viscosity properties, and that the desirable saturates can be segregated from the undesirable satu rates by the use of a solid adsorbent. It has also been found that certain components of the aromatic fraction possess desirable viscosity properties and are even superior to some of the saturate components, and that the desirable aromatics can also be segregated from the undesirable aromatics by the use of a solid adsorbent. Stillfurther, it has been found that'an improved lubricating oil'. composition can be obtained by blending the desirable saturates with the desirable aromatics.

Accordingly, theprocess of the present invention comprises subjecting a lubricating oil fraction to treatment.

with a solid adsorbent and recovering therefrom the saturated components having a refractive index (n of. belowabout 1.485, which components are the de sirable saturates, separate from other saturates. According to a. preferred embodiment, a lubricating oil fraction is subjected to treatment with a solid adsorbent to recover from the fraction the saturates having a refractive index (11 of below about 1.485, and preferably below about 1.480, and to recover separately the aromatics having a refractive index (11 below about 1.525, and preferably below about 1.515, separately from other aromatics, and the recovered saturates and aromatics. are blended to produce a high viscosity'index lubricating. oil.

The invention will be better understood from a consideration of the data given in Table I. The data were obtained by introducing 200 parts by weight of art-East Texaslubricating oil distillate fraction having a'viscosityof about 250 Saybolt Second Universal (SSU) at 100 E, into a column containing silica gel, the gel-to-oil ratio being about :1, thereby substantially completely adsorbing the oil on the silica gel, and then passing The invention also relates to improved lubricating United States Patent 0 I ately preceding saturate fraction.

2,756,197 Patented July 24, 1956 sorb the oil. Thirty successive fractions were collected and the isopentane was separated from each fraction by distillation.v The weight and refractive index of each solvent-free fraction are shown in Table I.

TABLE I Parts by Refractive Weight of Index (ne of Type Fraction Solvent- Solvent-Free Component Free Fraction Fraction 25. 7 1. 4658 Saturate 44. 1.4723 Do. 39.6 1.4850 D0. 5.7 1.5120 Do. 1. 0 1. 5038 Olefin. 0.7 1. 4984 Do. 1. 3 1. 5000 Aromatic 1,4 1.5019 D0. 2.3 l 5030 D0. 2.8 1 5038 Do. 3.0 1 5054 D0. 3.0 l 5094 Do. 4. 15 1 5163 Do. 5.6 1 5278 D0. 5.35 1 5393 Do. 4. 1 5518 Do. 4.45 1 5594 D0. 4.05 1 5682 Do. 3. 45 1.5785 D0. 3.1 1.5850 D0. 2.75 1 5900 DO. 3. 60 1 5920 D0. 3. 15 1 6060 Do. 3.3 1 6160 Do. 4.1 l 6190 Do. 4.4 Do. 2. 6 1 6158 Do. 2.2 1 61.35 D0 2.2 1 6067 .DO. 1. 60 Resin.

Referring to'Table I, it will be noted that the refractive index of the first fractions to be desorbed, the saturated components (which are primarily alkyl naphthenes in the case of dewaxed lubricating oil fractions), increases with increasing adsorbability until the refractive index reaches a maximum, which indicates the saturate components of highest naphthenicity. The next fraction desorbed, after the saturates, is the olefin fraction, the refractive index of which is lower than the immedi- In this case, the olefin content of the lubricating oil was relatively very small. At the point of minimum refractive index, the aromatics begin to be desorbed or eluted. The refractive index of the aromatic fractions increases with increasing adsorbabilityuntil a maximum is reached which indicates the componentsof highest aromaticity.

In greater detail, the process of the present invention comprises substantially completely adsorbing a lubricating oil fraction on a solid adsorbent, preferably a silica gel, the adsorbent to oil ratio being at least 10:1, and preferably at least 20:1, and then treating the solid adsorbent having the oil adsorbed thereon with a suitable desorbing agent or eluent, such as a low molecular weight saturated non-aromatic hydrocarbon having from about 3 to about 10 carbon atoms per molecule, to desorb those saturated components having a refractive index of less than about 1.485, and preferably less than about 1.480. According to a specific embodiment of the invention the desorption orelution is continued to remove the remaining saturates and the olefins, which saturates and olefins are rejected, and is further continued to recover, as product, those aromatics having a refractive index of less than about 1.525, and preferably less than about 1.515. The recovered desirable aromatics are then blended with the recovered desirable saturates to pro duce a high viscosity index lubricating oil. From the standpoint of viscosity index, the olefins can be collected' with the desirable aromatics, and the mixture of olefins and aromatics can then be blended with the deu sirable saturates. However, it is generally preferred to reject the olefins since they are extremely unstable to oxidation.

The high viscosity index aromatics usually do not have as high a viscosity index as the high viscosity index saturates and, therefore, the blend of desirable aromatics and desirable saturates will have a slightly lower viscosity index than the desirable saturates alone. However, since the aromatics contribute to engine cleanliness, it is preferred to blend them with the high viscosity index saturates.

The invention is particularly applicable to the refinement of dewaxed and deasphalted lubricating oil distillates, such as East Texas and Ventura distillates. The invention can also be used for improving the viscosity index characteristics of white oils and of lubricating oil rafiinate fractions obtained by the selective solvent extraction, e. g., extraction with liquid sulfur dioxide, phenol, furfural, or the like, or by the Duosol process using, for example, propane and cresylic acids, of naphthenic and mixed base lubricating oil distillates. The invention can be employed for refining relatively wide boiling range fractions, such as bulk distillates, for example, distillates having a boiling range from about 400 C. to about 600 C., but it is preferably employed for refining narrower boiling range fractions, such as fractions having a boiling range from about 450 C. to about 550 C.

Any adsorbent which exhibits substantial selectivity between the components of the lubricating oil fraction to be treated can be employed. Preferably an adsorbent which has a high adsorption capacity and a high degree of selectivity between the components of the charge mixture is used. Silica gels, for example, silica gel, silica-alumina gel, and the like, and activated carbon have adsorptive properties which are especially suitable for producing high quality lubricating oils according to the process of the present invention. It is preferred that the absorbent used be finely divided to a particle size of 60-200 mesh size.

Any suitable desorbing agent can be used to displace the various hydrocarbon components from the solid adsorbent. Itis preferable to use as the desorbing agent a solvent which has complete miscibility with the charge l desired saturates and aromatics have been collected, sep arate from the undesirable fractions, the solid adsorbent is further treated with the desorbing agent to displace. the remaining components. The solid adsorbent can then be reused for treating further portions of the lubricating oil. It is preferred to subject the solid adsorbent, after the desorption operation, to steaming to remove any residual organic material. In a continuous process, the adsorbent is utilized in the form of a moving bed. The adsorbent is introduced into the adsorption zone and is passed therethrough in the form of a moving bed. A stream of inbricating oil is continuously fed to the adsorption zone.

The adsorbent, containing the lubricating oil substantially completely adsorbed thereon, is then introduced into a desorption zone and therein treated with a suitable desorbing agent to displace successively the various components of the oil. The desirable saturates and aromatics are collected, and the undesirable fractions are rejected. The treated solid adsorbent is then returned to the adsorption zone. The desorbed components are suitably separated from the desorbing agent, as by distillation. The process is generally carried out at ambient temperatures.

If the viscosity of the charge stock is undesirably high, the charge stock can be diluted with any suitable diluent, preferably the same material which is used as the desorbing agent.

The advantages of the present invention will be illustrated by the following examples:

Example. I

Two hundred parts by weight of an East Texas lubricating oil distillate having a viscosity of about 250 SSU at 100 F. was substantially completely adsorbed on silica gel, the gel-to-oil ratio being about 30:1. The adsorbent was then treated with isopentane to desorb four successive fractions of saturated components and one fraction of aromatics. The isopentane was removed from each of the fractions by distillation. The properties of each of the five solvent-free fractions, of the total saturate fraction, and of the saturated components separated in accordance with the present invention are given in Table II.

stock at all concentrations. When distillation is to be used to remove the desorbing agent from the product, it should have a boiling point substantially different from the charge components to permit ready separation. The desorbing agent used is preferably a low molecular weight saturated non-aromatic hydrocarbon having from about 3 to about 10 carbon atoms per molecule. Suitable desorbing agents include the alkanes and cycloalkanes, such as isopentane, isobutane, hexane, heptane, petroleum ether, cyclopentane, cyclohexane, and the like.

The process of the present invention can be carried out either as a batch process or a continuous process. In a batch process, the lubricating oil fraction to be treated is introduced into a stationary column of the solid adsorbent until the capacity of the solid adsorbent for adsorbing further portions of lubricating oil is exhausted. The desorbing agent is then passed through the solid adsorbent containing the oil adsorbed thereon to selectively desorb the various fractions in succession. After the According to the process of the present invention, saturate fractions 1 and 2 are preferably collected, and fractions 3 and 4 rejected. From the data given in Table II, it can be seen that the viscosity index of the portion of the saturates selected in accordance with the present invention is 18 units higher than that of the total saturate fraction. Fraction 3, which has a refractive index of 1.4850 is on the borderline between the desirable and the undesirable saturates, and, if desired, it can be admixed with fractions 1 and 2. Fraction 5 represents a desirable aromatic fraction. Fraction 5 is preferably blended with the desirable saturate fractions.

Example ll Two hundred ten parts by weight of a Ventura lubricating oil distillate having a viscosity of about 60 SSU at 210 F. was substantially completely absorbed on silica gel, the gel-to-oil ratio being about 30:1. The adsorbent was then treated with isopentane to desorb five successive fractions. The isopentane was removed from achlof the fractions. by distillation; Thepmpertie's and disposition; of each of the solvent-free fractions are given in Table III.

G We claim as our invention; r p v 1:;A method of produci high viscosity hideilw bricatin'g' oil which comprises contacting a lubricating oil TABLE III Visat" Vis. at I Traction -Parts by m 100 F. 210.F. Hydrocarbon VI Disposition wt. (centi- (centi- Type stokes) stokes) 62. 2, 1.4645-L4756 45. 25 6.50 saturates. 103 Keep. 32.0 1.49091.6109 2,740 13. 59 "1nd 1,766 Discard 19. 9 1. 5164 175.1 10. 81 13 Keep. 16.5 1.5294 281.3 12.63 .(1 31 Discard All fractions desorbed after fractiOn S were discarded since the viscosity index became progressively more" negative.

Example 111 One hundred eighty-one parts by weight of a Ventura A The isopentane was removed from fraction with a silica gel, the gel-to-oil ratio being, at least about 20:1, whereby'sub'stantially all'of the-oil fraction is adsorbed on thesilica gel, treating said'silica gel with a saturated non-aromatic hydrocarbon having from about 3 to about 10 carbon atoms to separately desorb from said silica gel all of the saturated components of the lubricating oil fraction having a refractive index (n of below about 1.480 as one fraction, and desorbing the aromatic components of the lubricating oil fraction having a refractive index (n of below about 1.515 separate from all other components as another fraction, and blending said one fraction and said other fraction to obtain a high viscosity index lubricating oil.

2. The method according to claim 1 wherein the ratio TABLE IV Vls. at Vls. at Fraction Parts by m, 100 F. 210 F. Hydrocarbon VI Disposition wt. (centl- (centi- Type stokes) stokes) 1 27. 7 1. 4669 39. Keep. 2..- 38.8 1.4820 81.92 Do. 3. 14.1 1. 5081 1, 916 Discard. 4- 21. 7 1. 5070-1. 5251 169. 3 Keep. 5 7. 6 1. 5335-1. 5401 425. 7 Discard. Orig. Dis 1. 5242 225. 5

All fractions desorbed after fraction 5 were discarded since the viscosity index became progressively more negative.

Example IV Two hundred parts by weight of an East Texas lubricating oil distillate having a viscosity of about 250 SSU at 100 F. was substantially completely adsorbed on silica gel, the gel-to-oil ratio being about 30:1. The adsorbent was then treated with isopentane to desorb six successive fractions. The isopentane was removed from each of the fractions by distillation. The properties and disposition of each of the solvent-free fractions, the properties of the blend of desirable saturates and desirable of silica gel to said lubricating oil fractions is about 30:1.

3. A method of producing a high viscosity index lubricating oil which comprises contacting a lubricating oil fraction with a silica gel, the ratio of silica gel to oil desorb from said silica gel all of the saturated components of the lubricating oil fraction having a refractive index (n of below about 1.485 as one fraction, and desorbing the aromatic components of the lubricating oil fraction having a refractive index (n of below about aromatics and the properties of the original distillate are 1525 Separate from all th r C mp nents as another given in Table V.

fraction, and blending said one fraction and said other TABLE V Vis. at Vis. at Fraction Parts by an 100 F. 210 F. Hydrocarbon VI Disposition wt. (centi- (centi- Type stokes) stokes) 83. 8 1. 47031. 4806 60.89 7. 78 Saturates 100 Keep. 20. 3 1.4905 203.9 do 39 Discard.

2. 5 1. 5018 716. 2 d -29 Do. 12.4 1. 4984. 511 149. 7 50 Keep. 16. 3 1. 528-1. 533 547. 2 6 -25 Discard.

3. 4 1.5737 8,437 39. 76 .do -523 Do. 6. 66. 63 8. 26 Saturates 101 Aromatics. Orig. Dist.-. 177.64 12. 11 46 All fractions desorbed after fraction 6 were discarded since the viscosity index became progressively more negative. It will be noted that the blend of the desirable aromatics and the desirable saturates possessed a viscosity index as high as that of the saturates alone.

fraction to obtain a high viscosity index lubricating oil. 4. The method according to claim 3 wherein the ratio of silica gel to said lubricating oil fractions is about 30:1. 5. A lubricating oil composition consisting essentially of a blend of saturated and aromatic fractions derived from a lubricating oil stock, all of the saturated components in the saturated fractions having a refractive index (11 below about 1.485 and all of the aromatic components of the aromatic fractions having a refractive index ,(n below about 1.525, said composition being free of saturated components having a refractive index (11 substantially greater than 1.485 and free of aromatic components having a refractive index (11, sub stantially greater than 1.525.

6. A lubricating oil composition consisting essentially of a blend of saturated and aromatic fractions derived from a lubricating oil stock, all of the saturated components in the saturated fractions having a refractive index (n below about 1.480 and all of the aromatic components, of the aromatic fractions having a refractive index (n below about 1.515, said composition being free of saturated components having a refractive index UNITED STATES PATENTS 2,509,486 Danforth 4. May 30, 1950 2,572,866 Jones Oct. 30, 1951 2,576,525 Lipkin Nov. 27, 1951 2,643,217 Watson et al June 23, 1953 2,674,568 Lillard Apr. 6, 1954 OTHER REFERENCES Hersh et al.: Ring Analysis of Hydrocarbon, MixturesfTJournal of the Institute of Petroleum, 36 (1950), page 625. 

1. A METHOD OF PRODUCING A HIGH VISCOSITY INDEX LUBRICATING OIL WHICH COMPRISES CONTACTING A LUBRICATING OIL FRACTION WITH A SILICA GEL, THE GEL-TO-OIL RATIO BEING AT LEAST ABOUT 20:1, WHEREBY SUBSTANTIALLY ALL OF THE OIL FRACTION IS ADSORBED ON THE SILICA GEL, TREATING SAID SILICA GEL WITH A SATURATED NON-AROMATIC HYDROCARBON HAVING FROM ABOUT 3 TO ABOUT 10 CARBON ATOMS TO SEPARATELY DESORB FROM SAID SILICA GEL ALL OF THE SATURATED COMPONENTS OF THE LUBRICATING OIL FRACTION HAVING A REFRACTIVE INDEX (ND20) OF BELOT ABOUT 1.480 AS ONE FRACTION, AND DESORBING THE AROMATIC COMPONENTS OF THE LUBRICATING OIL FRACTION HAVING A REFRACTIVE INDEX (N1D20) OF BELOW ABOUT 1.515 SEPARATE FROM ALL OTHER COMPONENTS AS ANOTHER FRACTION, AND BLENDING SAID ONE FRACTION AND SAID OTHER FRACTION TO OBTAIN A HIGH VISCOSITY INDEX LUBRICATING OIL,
 5. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A BLEND OF SATURATED AND AROMATIC FRACTIONS DERIVED FROM A LUBRICATING OIL STOCK, ALL OF THE SATURATED COMPONENTS IN THE SATURATED FRACTIONS HAVING A REFRACTIVE INDEX (ND20) BELOW ABOUT 1.485 AND ALL OF THE AROMATIC COMPONENTS OF THE AROMATIC FRACTIONS HAVING A REFRACTIVE INDEX (ND20) BELOW ABOUT 1.525, SAID COMPOSITION BEING FREE OF SATURATED COMPONENTS HAVING A REFRACTIVE INDEX (ND20) SUBSTANTIALLY GREATER THAN 1.485 AND FREE OF AROMATIC COMPONENTS HAVING A REFRACTIVE INDEX (ND20) SUBSTANTIALLY GREATER THAN 1.525. 